In an ad hoc wireless network, transceivers or “nodes” are arranged to communicate with each other without any network infrastructure or centralized administration. The arrangement can be static or dynamic, or combinations thereof. The nodes can be cellular telephones, portable computing devices, or special purpose devices such as sensors. The nodes in the network establish routing among themselves to form their own network. Due to a limited transmission range of the transceivers, messages from a source node may have to pass through one or more intermediate routing nodes before reaching a destination node.
In many ad hoc wireless networks, most, if not all of the nodes are battery powered. Therefore, minimizing power consumption is a primary concern. Some techniques for reducing power decrease transcoder complexities, use low power circuits and low signaling-cost routing protocols. Other techniques attempt to exploit the network topology to reduce power.
Heinzelman et al., in “Energy-efficient Communication Protocol for Wireless Micro-sensor Networks,” Proc. of the IEEE Hawaii Int. Conf. on System Sciences, pp. 3005–3014, January, 2000, describe communication protocols for power reduction in a wireless network. They describe a clustering based protocol that utilizes randomized rotation of local cluster heads to evenly distribute the power load among the nodes in the network. They also indicate that when the distance between two nodes is short, direct transmission is more efficient than multiple hop transmission.
Chang et al, in “Energy Conserving Routing in Wireless Ad-hoc Networks,” Proc. of IEEE INFOCOM 2000, March, 2000, describe methods for selecting routes and corresponding power levels in a static wireless network so that power consumption is reduced.
Catovic et al, in “A new approach to minimum energy routing for next generation multi-hop wireless networks,” Journal of Communications and Networks, Special Issue on “Evolving from 3G deployment to 4G definition,” December 2002, describe a technique for transmitting data over two different channels at different power levels. A rake receiver is used to reconstruct the original data by combining the two received signals.
Chen et al., “Energy Efficient System Design with Optimum Transmission Range for Wireless Ad-hoc Networks,” Proc of IEEE Int. Conf. on Communications, ICC'02, pp. 945–952, May, 2002, determine optimum transmission range and hop distances in wireless ad-hoc networks.
The prior art has not addressed the problem of bit error propagation through the multi-hop paths. To eliminate error propagation, the transmit signal power levels must be increased on multi-hop paths. As a result, overall power consumption in the network increases. On the other hand, at each intermediate node, a received signal can be decoded and re-encoded, and then forwarded to the destination or to the next intermediate node. This can prevent error propagation, at the cost of increasing power consumption due to complexities of the transcoding process.
Most important, deciding whether to simply amplify and transmit the data or to regenerate the data depends on the position of the intermediate node relative to the source and destination nodes, and the level of power loss. Therefore, there is a need for a system and method that can reduce power consumption in a wireless ad hoc network.